This is a competitive renewal of the New York Obesity Research Center (NYORC). The NYORC integrates the obesity research programs situated at the Rockefeller University, the St. Luke's-Roosevelt Hospital Center of Columbia University and Cornell Medical College. Objectives of the combined center include the following: (i) to bring together under the Center's aegis, a critical mass of independent investigators of separately funded research projects who share a strong interest in the study of obesity- related problems; (ii) to use funds available for support of pilot and feasibility (P/F) projects and program enrichment activities to promote and test new research ideas, stimulate productivity, foster the development of talented new investigators in the field, and persuade creative scientists working in areas or disciplines not ordinarily concerned with obesity to become involved in obesity-related research; (iii) to provide participating investigators of funded projects relevant to obesity research with valuable laboratory, technical and educational services that otherwise would not be available, thereby improving productivity and efficiency of their operations, and (iv) by maintaining a dynamic focus for obesity-related investigation, to move the field more effectively into basic and applied research critical to the solution of key problems. Ten Cores offer a comprehensive spectrum of services: funding is requested for 6 of them; (i) the Administrative Core which provides a structure for peer evaluation of P/F protocols, training initiatives, a Sub-Core for Biostatistical/ Computational Services and an enrichment program; (ii) a Body Composition/Energy Expenditure Core; (iii) a Core for measurement of Hormones and Metabolites; (iv) an Adipose Tissue/Molecular Biology Core; (v) an Ingestive Behavior Core; and (vi) a Mass Spectrometry Core. No funding is requested for the other four cores; (vii/viii) two Inpatient General Clinical Research Center Cores for conduct of rigorously controlled metabolic studies, one at St. Luke's Roosevelt and one at Rockefeller; (ix) an Outpatient Core for clinical investigation of obesity at St. Luke's- Roosevelt; (x) and a respiratory chamber-indirect calorimeter.